This invention relates to urethral pressure profilometry. More particularly, the instant invention comprises a catheter and a method of making same which is adapted for use in profilometry and which will simultaneously derive electrical signals from the urethra.
Malfunction of the complex urinary tract can result in a variety of objectionable and unfortunate problems. One of the most common problems associated with urinary dysfunction is incontinence, or the inability to volitionally control micturition.
One diagnostic technique for investigating urinary difficulties is profilometry, involving the generation of a urethral pressure profile. The urethral pressure profile is a graphical record of pressure within the urethra at successive points along its length. It is known, for example, that continence will be maintained if the intra-urethral pressure is greater than the intravesical pressure. Leakage of urine occurs when urethral pressure decreases to less than bladder pressure. The utility of the urethral pressure profile as a diagnostic technique is well known.
The generation of a urethral pressure profile involves the initial step of catheterizing a patient. The catheter must be connected to a source of fluid, such as carbon dioxide or water, and it must contain at least one discharge orifice for inputting fluid into the urethra. The input of fluid is maintained at a constant preset rate while fluid pressure is continuously monitored, and readings may be recorded on strip charts or the like. Fluid pressure varies directly with the resistance to flow, which, in turn, is due to the varying pressure exerted by the urethra covering the discharge orifices in the catheter. The urethral pressure profile will be derived as the catheter is withdrawn from the urethra. By displaying the results graphically, for example, a correlation of urethral pressure versus position within the urethra will be provided. The catheter is preferably withdrawn from the urethra at a constant velocity.
Catheters are generally comprised of soft rubber materials, such as latex or silicone rubbers. In the prior art it has been very difficult to accurately cut uniformly sized holes in silicone or latex materials because of the high elasticity and softness of same. Because of these characteristics the material will tend to give way or yield when a drill bit, for example, is applied, resulting in roughly formed holes of unpredictable diameter. In order to achieve quantitatively accurate results during profilometry, it is important to have fluid discharge orifices with smooth surfaces and uniform cross-sectional area, so that reproducible results are obtained with interchangeable catheters.
A prior art urethral catheter is shown in the U.S. Pat. No. 3,428,046, issued to Remer et al. on Feb. 18, 1969. An esophageal catheter is shown in U.S. Pat. No. 3,437,088, issued to L. Bielinski on Apr. 8, 1969. A multipurpose cathether on which a pair of electrodes are mounted is shown in U.S. Pat. No. 3,568,660, issued to N. Crites, Mar. 9, 1971. U.S. Pat. No. 3,815,611 shows a catheter on which a plurality of electrodes are mounted.
The hole drilling art as it relates to catheters is discussed in Urology, May 1975, Vol. V, No. 5.
Rigid catheter mounted electrodes for electromyography are shown in a copending application entitled "Method and Apparatus for Micturition Analysis," Ser. No. 566,044, filed Apr. 7, 1975, and owned by the same assignee as in this case. Interaction between rigid electrodes and the sensitive body tissues within the urethra normally causes objectionable patient pain as the catheter is slowly withdrawn from the urethra during generation of a urethral pressure profile. Even where significant pain is not produced with rigid electrodes, patient nervousness often results, yielding false or inaccurate diagnostic readings.